Many applications of sensor networks involve periodically collecting data generated by sensor nodes at the sink node. The periodical data collection on tree topology is a basic operation in a wireless sensor network. Such kind of many to one communication pattern is also defined as convergecast. In some applications, 100% packet delivery ratio is required for convergecast. Given single channel frequency, superframe specified in IEEE 802.15.4 provides GTS (guaranteed time slot) for contention free transmission. However, a method for assigning slot is not provided by IEEE 802.15.4, and especially the slot assignment in tree topology is a challenge.
Currently, most of the slot assignment methods for convergecast are centralized. In the centralized method, a central controller is required, and positions of all other nodes are also required. If the number of nodes is large, the centralized method will be invalid.
It should be noted that the above description of the background art is merely provided for clear and complete explanation of the present invention and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background art of the present invention.